As simply as it gets, how do you use mix paste properly. That is another thing I meant to ask, everytime I try to use it, the text are transparent and it will not let me use it. All I need to know is what it is for and what do I need to do to be able to use it.

First, just like the ordinary Copy and Paste, you need to select and copy some audio to the clipboard. Once you have done that you should be able to place your cursor somewhere else in the audio file and use Mix Paste to place the clipboard audio over the original audio mixing the two together rather than replacing it completely. You can choose the amount of each audio to mix in with the percentage sliders. There are also options for the type of Mix Paste you wish to do and where you want the copied audio to come from.

Lots of uses in audio restoration. I use it mainly for putting back background noise or room tone when restoring old film sound tracks where there are drop outs or when you have to overdo Noise Reduction to remove unwanted artifacts but it leaves the audio too clean, for instance. And in editing and patching dialogue. Adding a quick bit of reverb to a cut off note at the end of a piece of music.